Paper 1 · Number Theory
⏱ Tested in 2 exam questions since 2019
Lesson 3 of 5
Number Theory 3 Proof by contradiction: Prove root 2 is irrational
This tutorial is for members
Read the lesson notes free below — subscribe to watch the full worked video and download the PDF.
Subscribe for full access · €199/yrYou’ll learn
- Prove √2 is irrational by contradiction, assuming √2 = a/b in simplest form
- Justify the key step: a² even ⇒ a even
- Derive the contradiction that a and b share a factor of 2
- Finish with the explicit line 'therefore √2 is irrational' — it carries marks
Most recent exam questions
- 2023 P1 Q3(a)
- 2019 P1 Q6(b)
💬 Stuck on something in this lesson?
Send your question with this lesson’s name attached — you’ll get a reply by email.